This disclosure relates generally to turbomachinery, and in particular to manufacturing and machining of airfoils used in the turbomachinery.
Turbomachinery can provide efficient, reliable power for a wide range of applications, including aviation and industrial power generation. Aviation applications often include turbojet, turbofan, turboprop, and turboshaft engines. Gas turbine engines are rotary-type combustion turbine engines built around a power core made up of a compressor, combustor, and turbine arranged in flow series with an upstream inlet and downstream exhaust. The compressor compresses air from the inlet, which is mixed with fuel in the combustor and ignited to generate hot combustion gas. The turbine extracts energy from the expanding combustion gas, and drives the compressor via a common shaft. Energy is delivered in the form of rotational energy in the shaft, reactive thrust from the exhaust, or both.
Turbofan engines are commonly divided into high and low bypass configurations. High bypass turbofans generate thrust primarily from the fan, which drives airflow through a bypass duct oriented around the engine core. This design is common on commercial aircraft and military transports, where noise and fuel efficiency are primary concerns. Low bypass turbofans generate proportionally more thrust from the exhaust flow, providing greater specific thrust for use on high-performance aircraft, including supersonic jet fighters. Unducted (open rotor) turbofans and ducted propeller engines are also known, and are often utilized in a variety of counter-rotating and aft-mounted configurations.
Turbofan and turbojet engines are often subdivided into a number of stages, which are formed of alternating rows of rotor blade and stator vane airfoils. The airfoils are shaped to turn, accelerate, and compress the working fluid flow, or to generate lift for conversion to rotational energy in, e.g., a turbine. Accordingly, efficient engine performance depends upon precise control of the working fluid flow, including flow across fan, combustor, and turbine airfoils. Such precise control requires highly accurate manufacturing techniques to form the airfoil surfaces within specified design tolerances. To this end, material is typically removed from initially-forged or cast airfoils to meet design tolerances using sophisticated tooling systems, such as computer numerical control (CNC) machining systems. Often, the airfoil is secured within the tooling system using fixtures that prevent movement of the blade during material removal. However, in some cases, the airfoil can warp or otherwise deform upon release from the fixtures, possibly resulting in a finished airfoil that does not meet design specifications.